Vitreous glass sealed beam lamp units have been used for vehicle lighting since at least the 1930's in the United States. These lamps generally include a paraboloidal reflector having a highly mirrorized inner surface that usually has two central openings that receive connectors for a filament aligned within the reflector. The reflector is enclosed by a circular convex lens also constructed of glass that is located with respect to the reflector by various types of integral locating tabs and is joined to the reflector by heat fusion. The connector assemblies are also usually connected to the reflector by a heat fusion process, and the composition and pressure of gas within the reflector-lens envelope are carefully controlled through a filling tube formed integrally with the reflector, and thi1s tube is fused after evacuation and/or, inert gas filling of the lamp envelope. Controlling the atmosphere within the envelope through the filling tube is extremely costly, and the filling tube must be carefully fused at the proper instant to achieve the desired atmosphere within the envelope.
Such a sealed beam lamp unit is shown and described in the D. K. Right U.S. Pat. No. 2,148,312 dated Feb. 21, 1939.
These sealed beam lamp units, which must be replaced after the filaments burn out, require complicated locking rings and adjustment assemblies, permanently carried by the associated vehicle to hold them in proper position. The locking rings frequently include adjusting brackets for varying the attitude of the lamp units to properly adjust the lamp's beam to achieve the desired lamp alignment.
It has been suggested that the reflector of a rectangular sealed beam lamp unit be constructed of a plastic material with support flanges formed integrally with the plastic to eliminate the complicated mounting flanges and rings required in prior lamp units. Such a construction is shown in the Thomas T. Talon et al U.S. Pat. No. 4,188,655. This patent discloses a lamp with three integral flanges on a plastic reflector that cooperate with three adjusting assemblies mounted to the vehicle that permit adjustment of the lamp beam in two orthogonal planes. While such an arrangement is suitable for many passenger automobile applications it is nevertheless quite costly because of the three separate fastening and adjusting mechanisms required.
Because of the many problems in manufacturing vitreous sealed beam lamp units, halogen bulb units have become increasingly popular over the last several years. In halogen bulb lamp units, a halogen bulb sub-assembly is constructed that consists of a sealed gas filled bulb having leads, that provides high intensity illumination for the lamp. Because the halogen bulb sub-assembly is itself sealed, it is not necessary to accurately control the gas content within the reflector of these halogen bulb lamp assemblies and for that reason, among others, the manufacturing process is considerably simplified.
Many vehicles, particularly heavy trucks and large, off-the-road construction equipment, have 24-volt electrical systems which require 24-volt lamp assemblies. The filament required in a 24-volt halogen bulb is very tightly coiled and this increases the likelihood of adjacent coil turns in the filament contacting one another under even normal vibration occurring in the vehicular environment particularly in heavy trucks and off-the-road vehicles. When one or more of these adjacent coil turns of the filament comes in contact with another the resistance of the filament goes low, resulting in bulb burn-out. Thus, it has been found extremely difficult to manufacture a 24-volt halogen bulb sub-assembly for vehicular lamp units.
It is, therefore, a primary object of the present invention to provide a 24-volt vehicle halogen bulb lamp assembly that ameliorates the problems noted above with prior known 24-volt halogen bulb lamp units.